In my Google Chrome extension content script I have the following:
jQuery(document).ready(function() { var player = document.getElementById(\'player\');
Works fine for me in chrome 9.
Try this fiddle: http://jsfiddle.net/Ee7mq/
If the console doesn't show the player tag something is wrong with your browser. If it does, something is wrong with your code. To figure out what i'd need to see more of it.